Apparatus for feeding pulverized coal and air to alpha furnace



Oct. 25, 1932. E, TENNEY 1,884,378

APPARATUS FOR FEEDING PULVERIZED COAL AND AIR TO A FURNACE Filed Nov. 30. 1928 Zuerged Fuel 22 1 40 Zbrceri -dra7"i 1 I 4/ 4:7 49 i J2 1 5/ l i; J4 as ii i /8 INVElYlOR, a 8 atkund Xx BY mm KM 7 8 Mk1 ATTORNEYS.

Patented Oct. 25,1932

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EDWARD H. TENNEY, OF WEBSTERGROVES MISSOURI APPARATUS FOR FEEDING PULVERIZED CUAL AND AIR TO A FURNACE Application filed November so, 1928. serial No. 322,721.

This invention is a novel apparatus for feeding pulverized coal and air to a furnace, and has particular reference to the manner of supplying and mixing the necessary air of combustion with pulverized fuel supplied or fed from a storage container or bin, the mixture to be delivered into the combustion chamber of the furnace through a burner, for example for short flame combustion below a boiler. p

The main object of the present invention is to increase the efficiency of pulverized fuel combustion by the storage system, especially by insuring a thorough mixture of the fuel with the greater part of the air before it reaches the burner and combustion point. lhe invention isparticnlarly intended for use in boiler installations wherein the pulverized fuel is supplied from an overhead storage container or hopper. Experience has shown that there exists a difiiculty inobtaining proper mixture of the coal with sufi'icient air for complete and rapid combustion. It has been customary to supply a small portion of primary air to the fuel stream to assist its exit from the storage container, and to supply the balance or secondary air atthe burner or as the mixture is delivered into the combustion chamber. lVith this prior system it is impossible to rely on proper mixture and as a result the flame is apt to be long and combustion slow and incomplete. This shortcoming of the prior art is overcome in the present invention by supplying a considerable portion of the air to the fuel stream at a point well removed from the furnace or distant from the burner, so that in the extended passage to the 7 burner the fuel and air will become well mixed 40 before delivery.

Another ob ect of the invention is to regulate the proportion of air so supplied to the fuel stream between the bin and burner without creating any back pressure.

Other and further objects and advantages of the present invention will be pointed out in the following description. of an illustrative embodiment thereof or will be understood by those skilled in the art to which the invention relates. For the attainment of the objects and advantages referred to, the invention consists in the noval features of construction, combination and arrangement of parts hereinafter set forth, shown by way of illustration in the accompanying drawing, and specifically pointed out in the appended claims. 1 g

In the accompanying drawi g, Fig. 1 is a more or less diagrammatic vertical longitudinal sectional view of a furnace and pulverized fuel burning apparatus embodying the invention; and

Fig. 2 is a fragmentary sectional view on a larger scale, showing the means for regulating the supply of intermediate air to the fuel stream.

Referring now to the drawing in detail, it will be seen that the'combustion space or furnace chamber 4 is disposed behind a front wall 5 having apertures 6 through each of which the fuel and air are injectedfrom a burner to be described. The bottom of the furnace chamber is shown inclined," being defined by the hopper wall 7, on the upper side of which may be a system of water tubes 8, the forward ends of which extend through 75 the front wall 5 for connection with a header 9 which may be connected as part of the boiler. The inner side of the arch 10 has water tubes 11, the ends of 'which'are connected with externally disposed headers 12, also in circulation with the boiler. The wa- .ter tubes 13 of the boiler are disposed above the combustion chamber and are shown connected through a header 14; with a drum 15 in a. usual manner.

Across the front of the furnace are a plurality of burners 17 each fitted into a front wall aperture 6, and each containing an annular air passage 18 which surrounds a central fuel tube 19. At the delivery end of the burner is shown a spreader 20, which be rotary or fixed. and is adapted to whirl and spread the fuel and air streams as they leave the burner so as to enter the combustion chamber as a short wide angle flame.

Pulverized coal or fuel is stored in and delivered from an overhead bin or storage container 22. At the bottom of the bin 22 is a hopper outlet 23 through which the fuel flows to a mechanical fuel feeding device 24 of the type, for example, which comprises a casing within which is a rotatable feed screw driven by suitable reduction gearing within a gear box 26, the power for which is furnished from or by a motor 27. As the screw 25 rotates, it propels the pulverized coal axially into an elbow exit 31, aided by a stream of preliminary or primary air forced into the feeder 24 through an air inlet 28 supplied from an air pipe 29 leading from a forced draft manifold or air duct 30. The direction in which this primary air enters the fuel stream from the inlet 28 induces flow and tends to break up the fuel.

The bend in the elbow exit 31 turns the flow downward and from here the fuel stream passes downwardly through a down pipe 32, and a Y-fittiug 33 also supplied with forced draft air from duct and pipe 34. From the fitting 33 the flow is through flared pipe section 35 to an offset or bent pipe 36. The lower end of the down pipe 36 is connected with a straight length of pipe 37, the exit end 38 of which delivers into a larger passage to be described. The pipe 37 is shown extending into a special forced draft duct 40, for example through the upper wall of it. This air duct is shown disposed in front of and above the top of the furnace wall 5, and supplies a large volume of air for all of the burners. For the tight accommodation of the pipe 37, the duct 40 has a top fitting 41. An opening 42 is shown in the bottom wall of the duct 40, said opening leading to a passage larger in diameter than the end of the pipe 37 and concentrically surrounding the latter to provide an annular air passage 43 at this point, both 38 and 43 delivering into a down pipe 44.

Thus additional, or what may be termed intermediate, air in large quantities is supplied under forced draft to the fuel stream at a point well in advance of the burner 17. It induces fuel flow. and the air and fuel streams become thoroughly mixed in their combined passage through the length of the down pipe 44 and its curved extension 45, from which the mixture is conducted to the central fuel tube 19 of the burner.

It is important to regulate the amount or rate of flow of air forced into confluence with the fuel laden air below the annular passage 43, and a damper 47 is shown for this purpose, for example slidably mounted on the lower end of the pipe 37. This damper is in the nature of an annular plate slightly larger than and movable to and from the opening 42 and guided by strips 48 sliding on pipe 37, and for adjustment it has a piv otal connection with the yoke end of a damper lever 49 which is fulcrumed on a post 50 Within the duct. The other end of the lever 49 extends through a slot in the side wall of the duct, and is arranged to be moved up and down by means of an adjusting screw 51 which is threaded into a fixed. wall 52 and has a handle 54 for turning the screw, and which can be locked in adjusted position by a lock nut 53. By turning the screw 51 to move it either up or down, the lever 49 will be rocked about its fulcrum and will move the damper 47 correspondingly, as indicated by the dotted line positions shown in Fig. 2.

Secondary or final air may be supplied to the annular air space 18 in the burner through a conduit 55 leading from the forced draft duct 40. This secondary air is mixed with the fuel stream at the burner delivery as has previously been explained, both the streams being under the pressure of the same forced draft.

The operation of the improved apparatus has been indicated in the foregoing description and the advantages stated. The damper 4? may be regulated in conjunction with the speed of delivery of the feeder 24. As an example, from 5% to 10% of the total air may enter at the feeder, and from 50% up can be introduced and thoroughly mixed with the fuel beyond the passage43 before reaching the burner. The air introduced at the burner may be below 40% or as low as zero in some cases. These results are accomplished without causing any back pressure in the fuel delivery conduit, the forced draft air expediting the fuel flow. There is no danger from flashing back of flame into the apparatus. The novel structure is simple, and capable of being constructed, installed and operated with economy, and is rugged and durable. I

The invention is susceptible of modification in various features of construction, arrangement and operation, and the invention is not intended to be limited to such features except as specified in the appended claims.

What is claimed is:

1. Pulverized fuel burning apparatus comprising, in combination, an overhead storage container for pulverized fuel, a burner delivering into a combustion space, an air duct supplying forced-draft air, said air duct being provided with an opening in one wall, a fuel conduit connecting said opening with the burner, another fuel conduit leading from the overhead storage container and through the duct to discharge into the first mentioned fuel conduit, the discharge end of said second fuel conduit being smaller than said opening in the duct and smaller than the entrance end of the first mentioned fuel conduit, whereby an annular supply of air will be added to the fuel stream, and a damper adjustably mounted on the end of the second-mentioned fuel conduit to regulate the passage of such air through the opening.

2. Pulverized fuel burning apparatus comprising, i n combination, an overhead storage container for pulverized fuel, a burner delivering into a combustion space, an air duct supplying forced-draft air, said air duct being provided with an opening in one wall, a feeding device delivering pulverized fuel from the storage container, a conduit for conveying the fuel from said feeding device through the duct and its opening, means for introducing primary air to said conduit adjacent to the feeding device, another conduit connecting the opening in the duct with the burner, the opening in the duct and the entrance end of said other conduit being larger than and concentric with the discharge end of the first-mentioned conduit, whereby an intermediate supply of air will be injected annularly into the fuel stream, a damper mounted within the duct to regulate the flow of such intermediate air through said opening, and means for supplying secondary air to the fuel stream as it emerges from the burner.

8. Apparatus for conveying pulverized coal from a supply point, mixing it with air and delivering it to a furnace, comprising, a fuel supply pipe carrying downwardly a stream of fuel mixed with primary air, a relatively large forced-draft air duct having in one wall an opening larger than said pipe,

conduit extending from said duct wall opening with extended travel to the furnace, the said fuel supply pipe entering and traversing the duct and entering said duct wall opening and discharging into said conduit, and spaced to leave an annular air passage between the two, whereby the air flow from the duct to the conduit causes induced flow through the fuel supply pipe, and the combined streams are caused to mix during their extended travel to the furnace.

4. In combination with a storage container for pulverized fuel, and a burner delivering into a combustion space, an air duct supplying forced-draft air, said duct having in its lower wall an outlet opening, an elongated conduit extending from said opening to the burner, a feeding device delivering pulverized fuel from the storage container, and a fuel pipe leading from the feeding device and extending through a wall of the duct and terminating within the outlet opening of the duct, but spaced from the periphery of such opening, whereby air from the duct will be supplied in an annular stream surrounding the fuel stream passing from the pipe to the conduit.

5. 'In combination with a storage container for pulverized fuel, and a burner delivering into a combustion space, an air duct supplying forced-draft air, said duct having an outlet opening, a conduit extending from said opening to the burner, a feeding device delivering pulverized fuel from the storage container, a fuel pipe leading from the feeding device and terminating within the outlet opening of the air duct but spaced from the the air regulating means comprises a damper surrounding the fuel pipe and movable toward and from the outlet opening.

7. In combination with a storage container for pulverized fuel, and a burner delivering into a combustion space, a relatively large air duct supplying forced-draft air, said duct having an outlet opening at its under side, and a conduit therefrom to the burner, a feeding device giving regulated delivery of pulverized fuel from the storage container, a fuel supply pipe leading from the feeding device and extending into said duct and terminating within the outlet thereof but spaced from such outlet whereby air will be supplied in an annular stream to the fuel stream passing therethrough, a second conduit extending from said duct for supplying secondary air directly to the burner, an annular damper controlling the air supply to the first conduit, and an independently regulable damper controlling the air supply to the second conduit.

In testimony whereof, this specification has been duly signed by:

EDWARD H. TENNEY. 

